import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while (true) {
            //通过accept方法"接听电话",然后才能进行通信
            Socket clientSocket = serverSocket.accept();
            Thread t = new Thread(()->{
                processConnection(clientSocket);
            });
            t.start();
        }
    }

    //通过这个方法来处理一次连接,连接建立过程中涉及到多次请求的响应交互
    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s:%d] 客户端上线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
        //循环读取客户端的请求并返回响应
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {
            Scanner scanner = new Scanner(inputStream);
            while (true) {
                if (!scanner.hasNext()) {
                    //读取完毕,客户端断开连接
                    System.out.printf("[%s:%d] 客户端下线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
                    break;
                }
                //1.读取请求并解析
                String request = scanner.next();
                //2.根据请求计算响应
                String response = process(request);
                //3.把响应返回给客户端
                PrintWriter printWriter = new PrintWriter(outputStream);
                printWriter.println(response);
                printWriter.flush();

                System.out.printf("[%s:%d] req: %s, resp %s \n", clientSocket.getInetAddress(), clientSocket.getPort(),
                        request, response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer tcpEchoServer = new TcpEchoServer(9090);
        tcpEchoServer.start();
    }
}























